Gasification processes generally include reacting a carbonaceous feed material (e.g., coal, petroleum, or biomass) with oxygen and/or steam to produce carbon monoxide and hydrogen. The resulting carbon monoxide and hydrogen mixture is commonly called “synthesis gas” or “syngas.”
Syngas can have many industrial applications. For example, syngas may be burned directly in internal combustion engines for generating electricity or driving machinery. In another example, syngas may be used to produce methanol and hydrogen, which in turn may be converted into other useful industrial compounds. Syngas may also be converted into liquid synthetic fuels (e.g., diesel, gasoline, etc.) via the Fischer-Tropsch process and/or other syngas-to-liquid processes.
Conventional gasification systems include fixed-bed gasifiers, fluidized-bed gasifiers, or entrained-flow gasifiers. In fixed-bed gasifiers, the feed material forms a fixed bed through which a gasification agent (e.g., steam, oxygen, and/or air) flows in either a counter-current or co-current flow configuration. In fluidized-bed gasifiers, the feed material does not form a fixed bed but instead is fluidized in steam, oxygen, and/or air. In entrained-flow gasifiers, the carbonaceous feed material is first pulverized and then gasified with oxygen or air in a co-current flow configuration.
The foregoing types of gasifiers suffer from certain operational drawbacks. For example, fixed-bed gasifiers typically require the carbonaceous feed material to have high mechanical strength and be noncaking in order to form a permeable bed. As a result, certain feed materials may not be processed in fixed-bed gasifiers. The conversion efficiencies of fluidized-bed gasifiers may be low due to elutriation of the carbonaceous feed material. Further, entrained-flow gasifiers typically may not be economically operated at small scales and may require an increased amount of oxygen compared to other types of gasifiers. The increased requirement for oxygen can increase the energy consumption of the overall entrained-flow gasification process, resulting in a lower energy efficiency. Accordingly, certain improvements in gasification systems and processes are needed.